The present invention relates generally to fluid flow connections and, more particularly, to pipe-to-tank connectors in sewage discharge systems.
Numerous fluid flow systems employ fluid sumps to receive and retain fluid for a period of time. Many sewage discharge systems, for example, use holding tanks as a sump for waste fluids. Given the nature of the fluid carried to the holding tank and the proximity of the holding tank to the living environment, it is particularly important that the connections between the inlet pipe, outlet pipe and holding tank are securely fluid tight and reliable over long periods of time despite the system stresses imposed by the corrosive nature of the fluid and the vibrations transmitted into the fluid system.
Previously, fluid inlet connections to such holding tanks, for example, have employed cast iron fittings to join the plumbing pipes, typically formed from PVC material, to the holding tank, often formed from polyethylene or fiberglass materials. While those cast iron fittings could be durable for a reasonable period of time in many applications, prolonged contact with sewage fluid has been found to lead to corrosion, particularly of the bolt-through connectors that are often used to retained the fitting to the tank.
Moreover, in order to properly seal the connection, each holding tank configuration and inlet pipe size could require a specially formed cast iron fitting, since solvent welding of the connection (as typically used upstream in the PVC plumbing) has been unavailable or impractical given the diverse materials found at the connection. Over time, as holding tank configurations change to accommodate different spacial constraints and desired volumes, an ever larger inventory of cast iron fittings and tooling to form those fittings has been required for servicing.
Further, many fluid systems including the holding tanks have been redesigned to have less weight. Unfortunately, that weight reduction has sometimes been done with the result that the holding tank wall strength is less able to sustain the weight of the cast iron fittings. In addition, the relatively heavy weight of cast iron fittings has rendered them more costly to ship and more susceptible to damage during shipping.
Accordingly, it is an object of the present invention to provide an improved fluid connection arrangement for joining pipes to holding tanks and the like. Other objects include the provision of a holding tank connection assembly that:
a. is readily adaptable to a variety of tank configurations and sizes and pipe sizes,
b. is light weight and inexpensive to manufacture and install,
c. maintains a reliable, even seal against fluid leakage between the tank wall and the connector and pipe,
d. permits solvent welding of the pipe to the connector,
e. is less susceptible to corrosion when handling sewage fluid, and
f. is relatively easy to install or replace in the field.
These and other objects of the present invention are achieved by the provision of a universal holding tank connector fitting formed from thermoplastic material and having a pass-though hub that enters the holding tank wall and is retained thereto by a sealing collar and a threaded nut engaging the sealing collar within the tank. Conformal seals are disposed between the hub and collar and the tank wall, with the hub and collar themselves keyed to the particular tank wall configuration. The hub includes an internal passageway into the tank which is dimensioned to closely receive the particular pipe which is to be connected via a solvent weld and, in certain embodiments, an end stop to limit and positively locate the pipe penetration into the tank. The conformal seals are keyed to fit at predetermined locations on the hub and collar, and load concentrating configurations are formed along the sealing surfaces that facilitate even and reliable seal pressure when the fitting elements are compressed together. The fitting components are readily adapted to different applications by the interchangeability of mold inserts within the tooling used to make the fittings. Hub penetration depth into the tank is selectable via skip threading on the hub end.